PHILADELPHIA -- Carlos Zambrano always has been an emotional powder keg, but that was tolerable when he was among the five best starters in the game from 2004-07.

That act became less acceptable when, after signing a five-year, $91.5 million deal with the Cubs after the 2007 season, his talents eroded. After a lackluster season with a lackluster Marlins squad in 2012, Zambrano went unsigned in the offseason, as no team considered itself desperate enough to take a chance on the bombastic Venezuelan.

No team, that is, until the Phillies came calling this week.

Wednesday morning the Phils announced they have signed the 31-year-old right-hander to a minor-league contract and that he will report to Clearwater, Fla., for extended spring workouts this week. Although the details of the contract weren't announced, a source said that Zambrano has an out clause if the Phillies don't add him to the major-league roster by July 1.

That gives the Phillies six weeks to assess Zambrano, both on the mound and between the ears.

"We're just trying to add some starting pitching depth," assistant general manager Scott Proefrock said. "He's going to go to extended spring trainings, throw some bullpens and progress from there.

"No promises were made, just an opportunity to add some starting pitching."

The Phillies made the signing just hours before Roy Halladay underwent arthroscopic surgery in Los Angeles to fix to remove a bone spur and clean up rotator cuff and labrum damage in his right shoulder. The Phils also have been without left-hander John Lannan (sprained knee), whom Proefrock said remains a week away from throwing off a mound in Clearwater.

Although Jonathan Pettibone has done an impressive job in five starts since replacing Lannan, and Tyler Cloyd filled in nicely for Halladay in his first start last week, the Phillies would prefer to not go an extended amount of time with two inexperienced starters in the rotation.

"Would we have done this without Roy (having surgery)? I can't say that we wouldn't have," Proefrock said. "We talked about him and other guys to add depth and experience in Triple-A.

"We're taking a chance that's low-risk and hopefully high-reward."

In 35 games (20 starts) with the Marlins last season, Zambrano went 7-10 with a 4.49 ERA. He used to be effectively wild, but in 2012 he was merely wild (75 walks in 132 Ï IP). He was moved to the bullpen after going 5-9 with a 4.54 ERA as a starter, but despite a slightly lower ERA, Zambrano's overall numbers out of the bullpen actually were a bit worse.

"I saw down in Miami and it seemed like he still had pretty good stuff," Charlie Manuel said. "We'll see. ... My thoughts on him are that I haven't seen him. When someone tells me someone is doing good, and it's someone in baseball I respect, then I think, OK, that lights me up a little bit.

"But I like to see him for myself. I like to try and get a look at him, because I might be thinking a little differently than most people -- usually I am."

This offseason Zambrano pitched in the Venezuelan Winter League, then made a start for his home country in the World Baseball Classic in March, retiring the first nine batters he faced before allowing two runs in the fourth inning against Puerto Rico.

Almost as concerning, if not more so, is Zambrano's inability to keep his head on straight. In addition to altercations with teammates and coaches in the dugout, not to mention opposing players and umpires, the hot-tempered Zambrano had a 2011 meltdown during and after a bad outing against the Braves. Before the game had ended, he had cleaned out his locker and announced he was retiring. He later rescinded his statement, but the Cubs suspended him without pay for 30 days, then announced he wouldn't pitch for them for the rest of that season. By 2012, Chicago was sending him and $15.5 million to Miami for Chris Volstad, one of the worst starting pitchers in baseball over the previous three seasons.

There was a time when you didn't need a second hand to count the number of starters better than Zambrano.

In the four seasons from 2004-07, there were four pitchers who had ERAs below 3.50 and 700 or more strikeouts: Johan Santana, Zambrano, Roy Oswalt and Brandon Webb. It's worth noting that all four of those pitchers are not in the majors anymore. Santana made just 21 starts since 2010 and his career is likely over at age 33. Webb made his final big-league start in 2009 prior to his 30th birthday. Oswalt, 34, has become a half-season rent-a-starter the last two years.

As the fourth member of that star-crossed quartet, Zambrano's trying to show his talent hasn't flamed out and that his temper perhaps has.

"I think in this situation we have a feel for his desire to come back and his sincerity about that," Proefrock said. "We're not signing him to a $90 million deal like the Cubs were, but you still want to make sure you get a guy who is committed and going to conduct himself appropriately, and as far as that's concerned we are satisfied."